#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main() {
	int i = 0;
	int j = 0;
	double m = 0;
	double n = 0;
	double sum = 0;
	for (i = 1; i <= 99; i += 2) {        
		m += 1.0 / i;
	}
	for (j = 2; j <= 100; j += 2) {        
		n -= 1.0 / j;
	}
	sum = m + n;                          
	printf("%lf\n", sum);         
	return 0;

}
